Your nylon leggings shed microplastics every time you wear them. Not occasionally. Every time.
Nylon is a synthetic polymer, which means it is plastic in fiber form. For women looking for non-toxic workout clothes, that fact has consequences worth understanding before the next purchase.
What Nylon Actually Is
Nylon was developed by DuPont in the 1930s as a petroleum-derived synthetic fiber. It is a polyamide, a type of polymer made by linking chemical units called amides together into long chains. The result is a strong, stretchy, moisture-wicking fiber that has dominated activewear manufacturing for decades.
It is also, structurally, a plastic. The same class of material as a plastic bottle, a synthetic rope, or a food storage bag. The fact that it has been processed into a fine fiber does not change its fundamental polymer chemistry.
How Nylon Releases Microplastics
Microplastics are small plastic particles less than 5 millimeters in size, including particles far smaller than that. When nylon fabric is worn, washed, or mechanically stressed, it sheds tiny fragments and fibers. These are called microfibers when they come from textile sources, and they are a subcategory of microplastics.
Research published in Environmental Science and Technology (Browne, M.A., et al., 2011) was among the first to systematically document microfiber shedding from synthetic textiles and identify washing as a primary release pathway. A single wash of a synthetic garment can release hundreds of thousands of fibers, many of which pass through wastewater treatment systems and enter waterways.
Nylon specifically has been identified as a significant microfiber contributor. A study published in Science of the Total Environment (De Falco, F., et al., 2019) analyzed microfiber shedding from multiple synthetic fabrics and found nylon among the consistent shedders, alongside polyester. The physical structure of nylon, with its smooth surface that does not bond fiber ends securely, makes shedding during mechanical stress a structural property of the material, not a manufacturing defect.
Shedding does not only happen in the wash. Research has documented microfiber release from synthetic fabrics during wear, including through friction and movement. A study in Environmental Science and Pollution Research (Pirc, U., et al., 2016) found that mechanical abrasion during normal use causes measurable fiber release. In activewear, which is worn during high-friction, high-movement activity and pressed close to the body throughout, that shedding happens in direct contact with your skin.
Where Those Microplastics Go
Microfibers shed during washing predominantly end up in waterways. Wastewater treatment plants capture some fraction, but even the sludge produced by that capture process is often applied to agricultural land, providing a secondary route back into soil and water systems. Research published in Nature Reviews Earth and Environment (Horton, A.A., et al., 2022) documented microplastic contamination across freshwater, marine, and terrestrial environments, with textile microfibers as a primary contributor.
The microplastics shed during wear go somewhere more immediate. They settle on surfaces, enter indoor air, and are available for inhalation and skin contact. The concentration of microfibers in indoor environments is consistently higher than outdoor concentrations, partly because synthetic textiles shed continuously into enclosed air spaces. People wearing nylon activewear through a workout class, commute, or full day of movement are contributing to that concentration in the spaces they occupy.
And beyond air and water, the research on human body burden is accelerating. Leslie et al. (2022), in a study published in Environment International, detected microplastics in human blood samples, indicating systemic absorption is occurring across the population. Ragusa et al. (2021), also in Environment International, found microplastic particles in human placental tissue. The long-term health implications of this internal accumulation are still being characterized, but the fact of accumulation is no longer in dispute.
Nylon and PFAS
There is a second issue with nylon beyond microplastics. Many nylon activewear garments are treated with durable water repellent coatings, stain resistance treatments, or odor-control finishes. Historically, many of these treatments relied on PFAS chemistry. The EPA has noted that PFAS exposure has been associated with thyroid disruption, immune system effects, and certain cancers in human studies. While many brands have moved away from long-chain PFAS, replacement chemistries are not always fully characterized for safety, and the label PFAS-free on finished activewear is not always independently verified.
Nylon itself does not require PFAS to perform its core functions. But in the activewear category, nylon garments are frequently sold with performance finishes that introduce this second layer of chemical exposure on top of the microplastic shedding question.
What the Nylon Alternative Looks Like
TENCEL Lyocell is not a synthetic polymer. It is a cellulosic fiber derived from plant-based cellulose, processed using a closed-loop system with a non-toxic solvent. It does not shed plastic microfibers. When TENCEL fibers break down from wear or washing, they release cellulosic fragments that are biodegradable, not petroleum-derived plastic particles.
The moisture management story is also different. Nylon manages moisture by wicking it along the surface. TENCEL Lyocell absorbs moisture into the fiber's core structure, which supports more stable thermoregulation and reduces the surface-level bacterial growth that causes odor in synthetic garments. Kaplan et al. (2014), in Fibers and Polymers, documented TENCEL's performance advantage in moisture management and thermal comfort in active wear settings. For the full comparison of how these two fabrics stack up, synthetic activewear versus TENCEL covers the detail. For the broader microplastic picture, whether polyester sheds microplastics covers the most prevalent synthetic. The full workout clothes microplastic question is also documented. And for a broader look at the chemical concerns in activewear, toxic chemicals in workout clothes covers what else is in the fabric beyond the fiber.
Bellissima's Sempre Leggings use 92% TENCEL Lyocell and 8% spandex for stretch. The spandex content means this is not a zero-synthetic garment, and that is stated clearly. What it is not is a nylon garment. The primary fiber is not a plastic polymer, and it does not carry the microfiber shedding profile that nylon does.
A Question Worth Asking
The activewear industry built itself on nylon because the performance properties are real. It stretches, it wicks, it holds shape. Those are legitimate qualities.
The microplastic question adds a cost to those qualities that was not visible for most of nylon's history as a material. That cost is now visible, and the research documenting it continues to grow.
The question is not whether nylon performs. It is whether what you are willing to trade for that performance profile still makes sense when you know what you are trading.
Sources
Browne, M.A., et al. (2011). Accumulation of microplastic on shorelines worldwide: sources and sinks. Environmental Science and Technology, 45(21).
De Falco, F., et al. (2019). Microfiber release to water, via laundering, and to air, via everyday use. Science of the Total Environment.
Pirc, U., et al. (2016). Emissions of microplastic fibers from microfiber fleece during domestic washing. Environmental Science and Pollution Research.
Horton, A.A., et al. (2022). Microplastics in freshwater and terrestrial environments. Nature Reviews Earth and Environment.
Leslie, H.A., et al. (2022). Discovery and quantification of plastic particle pollution in human blood. Environment International, 163.
Ragusa, A., et al. (2021). Plasticenta: First evidence of microplastics in human placenta. Environment International, 146.
Kaplan, S., et al. (2014). Thermal comfort of lyocell and other fibers in active wear. Fibers and Polymers, 15(6).
